1. The Field of the Invention
This invention relates to dyes and particularly to novel 2:1 chrome-complexed yellow dyes having a silver halide developing capability and also relates to photographic products and processes using the novel dyes.
2. Description of the Prior Art
Metal-complexed dyes are old and known to the art. One group of metal-complexed dyes are those referred to in the art as 1:1 complexes, a term embracing complexes of one dye molecule complexed to a metal ion. Metal-complexed dyes having two dye molecules complexed to a metal ion are also known to the art and are referred to as 2:1 complexes. For example, U.S. Pat. No. 3,730,725 describes a 2:1 chrome-complexed red dye. In general, 1:1 metal complexes of a given dye molecule and a metal have narrower absorption spectra and brighter color than a 2:1 complex of the same dye and metal. The corresponding 2:1 complex generally exhibits a rather broad absorption spectrum and dull color.
Metal-complexed dyes having a silver halide developing capability, e.g., metal-complexed dye developers, are also known to the art and are described, for example, in U.S. Pat. Nos. 3,218,164; 3,453,107; 3,482,972; 3,544,545; 3,551,406; 3,597,200; 3,705,184; 3,752,836 and 3,857,855 among others.
Above-mentioned U.S. Pat. Nos. 3,597,200; 3,705,184 and 3,752,836 particularly relate to 1:1 chrome-complexed yellow dye developers which can be illustrated schematically as follows: EQU DYE-CHROMIUM-LIGAND DEVELOPER.
Particularly useful 1:1 chrome-complexed yellow dye developers are described in referenced U.S. Pat. No. 3,705,184 and these conform to the following formula: ##STR3## where x can be 1-3, Z can be 1-3, (alkoxy) has from 1-8 carbon atoms and (alkylene) contains 1-6 carbon atoms.
A specific dye developer of Formula A having especially efficient performance characteristics and one which has enjoyed extensive commercial success is the 1:1 chrome-complexed yellow dye developer of the formula: ##STR4##
The present invention provides novel 2:1 chrome-complexed yellow dyes having a silver halide developing capability. As a class, the novel 2:1 chrome-complexed dye developers of the invention have desirable performance characteristics especially when employed in diffusion transfer photographic products and processes. As will be demonstrated later, certain 2:1 chrome-complexed dye developers within the class presented have performance characteristics comparable to and in certain respects, superior to those of 1:1 chrome complexed yellow dye developers of Formulae A and B.